As a young Congressman in 1984 he confessed to the Washington Post: “I have an enormous personal ambition. I want to shift the entire planet.” He has certainly shifted the Republican presidential primary race, though his victory over Mitt Romney in South Carolina will have the Washington establishment holding its head in its hands.

“He is very erratic and has very few friends inside the Beltway,” said a former White House official who served in two Republican administrations.

“People don’t trust him and don’t like him. There are a lot of serious conservatives right now just thinking 'please no’.” That establishment contempt was demonstrated best by Peggy Noonan, the columnist and former Reagan speech writer, who described the portly, mop-haired Gingrich as an “angry little attack muffin” after yet another petulant remark on the campaign trail.

With Gingrich, the problem is not policy but personality. He sees himself as the philosopher-king of the Republican Party, while former colleagues see him as a wayward, self-serving narcissist.

Those concerns led fellow Republicans to rebel and topple him as Speaker of the House in 1998, a year after he was fined £200,000 for ethics violations involving the use of tax-deductible funds for political purposes.

As Rick Santorum, a rival in the primaries, suggested during a debate last week, Gingrich is regarded by those who have worked with him as too unpredictable to be trusted with the highest office in the land.

“Grandiosity has never been a problem with Newt Gingrich. He handles it very, very well,” Mr Santorum remarked acidly, adding of the Gingrich speakership: “It was an idea a minute, no discipline, no ability to be able to pull things together.”

The 2012 Gingrich campaign has amply displayed his weaknesses as well as his strengths. His entire senior staff deserted him in the summer when he kept ignoring their advice to follow his own or that of Callista, his wife.

His refusal to cancel the couple’s romantic Greek island cruise was the last straw.

He later failed to gain the signatures needed to put his name on the ballot in Virginia, his home state. He was then criticised for comparing the failure to Pearl Harbor because the setback, he said, would inspire a heroic comeback. The episode did not suggest a Gingrich White House would run like clockwork.

He has run largely on his wits, but they have served him well and in South Carolina they made all the difference. Two debate performances showed that his finger is firmly on the pulse of conservative America and that he can rouse passions like no one else in the race, particularly the steady, unexciting Mitt Romney.

Born Newton Leroy McPherson in 1943 in Pennsylvania, he grew up as the son of his stepfather Bob Gingrich, a US army officer stationed in the United States, France and Germany.

In his first year as a history professor at West Georgia College Mr Gingrich pronounced that he wanted to become college president. Though he failed, he was determined to enter Congress and at the third attempt succeeded, going on to represent his home state for 20 years.

When he arrived in Washington, he became a laughing stock among some colleagues who mocked him as “Newt Skywalker” for his futuristic dreams, like mining on the Moon.

But early on, he predicted he would become Speaker and it was he who laughed longer.